Individual microphone elements designed for far field audio use can be characterized, in part, by their pickup pattern. The pickup pattern describes the ability of a microphone to reject noise and indirect reflected sound arriving at the microphone from undesired directions. The most popular microphone pickup pattern for use in audio conferencing applications is the cardioid pattern. Other patterns include supercardioid, hypercardioid, and bidirectional.
In a beamforming microphone array designed for far field use, a designer chooses the spacing between microphones to enable spatial sampling of a traveling acoustic wave. Signals from the array of microphones are combined using various algorithms to form a desired pickup pattern. If enough microphones are used in the array, the pickup pattern may yield improved attenuation of undesired signals that propagate from directions other than the “direction of look” of a particular beam in the array.
For use cases in which a beamformer is used for room audio conferencing, audio streaming, audio recording, and audio used with video conferencing products, it is desirable for the beamforming microphone array to capture audio containing frequency information that spans the full range of human hearing. This is generally accepted to be 20 Hz to 20 kHz.
Some beamforming microphone arrays are designed for “close talking” applications, like a mobile phone handset. In these applications, the microphone elements in the beamforming array are positioned within a few centimeters, to less than one meter, of the talker's mouth during active use. The main design objective of close talking microphone arrays is to maximize the quality of the speech signal picked up from the direction of the talker's mouth while attenuating sounds arriving from all other directions. Close talking microphone arrays are generally designed so that their pickup pattern is optimized for a single fixed direction.